A big milestone today as Google’s Chrome hits a cool 20 percent web usage share according to StatCounter numbers for the month of June (via TNW) based on aggregate data collected from their network of three million websites.

For the first time ever, Chrome passed the 20 percent mark globally, accounting for 20.65 share of all web browsing the world over. Compare that to just 2.8 percent in the year-ago period. Google’s browser is now chasing Firefox which fell from 30 percent in June 2010 to 28 percent in June 2011. All versions of Microsoft’s Internet Explorer have also fallen to 44 percent globally, down from 59 percent in June 2010.

In the United States Chrome’s rise was less rapid, hitting 16 percent in June while Microsoft’s and Mozilla’s browsers scored 46.5 percent and 24.7 percent, respectively. What’s especially interesting is Chrome’s share in South America where it grabbed 29.72 percent of the market, beating Firefox (24 percent) to the browser punch (Microsoft’s browser had 44.1 percent share). An indication of things to come globally?

The United Kingdom, for example, is the leading European market and traditionally the core territory for Mozilla’s browser which in Europe has always enjoyed the widest lead over rival browser vendors. In June, Google’s and Mozilla’s browser were tied with 21.6 percent share each in the country (IE: 46.4 percent). The decline of Internet Explorer and Firefox suggest that Chrome is gaining ground at the expense of its rivals around the world. The rise of Chrome is also a big boost for the WebKit rendering platform, the de facto standard in mobile but no so on desktops.